High-vacuum pump



Sept. 7, 1965 H. HUBER 3,204,860

HIGH-VACUUM PUMP Filed March 50, 1959 7 Sheets-Sheet 1 INVENTOR H- HUBER Sept. 7, 1965 H. HUBER 3,204,860

' HIGH-VACUUM PUMP Filed March 30, 1959 7 Sheets-Sheet 2- lNVENTOR H-HUBER BY 2414/ W ATTORNEYS Sept. 7, 1965 H. HUBER HIGH-VACUUM PUMP 7 Sheets-Sheet 3 Filed March 30, 1959 INVENTOR H-HUBER BY 7 I ATTORNEYS Se t. 7, 1965 H. HUBER 3,204,860

HIGH-VACUUM PUMP Filed March 30, 1959 7 Sheets-Sheet 4 I l l l I I I I H OOOOOOOOO OOQ'OOQOQOB c0 00 uooooc OOOQOOOOOQOQ INVENTOR H- HUBER Sept. 7, 1965 Filed March 50, 1959 H. HUBER 3,204,860

INVENTOR H- HUBER BY M 1 ATTQ RN 5Y5 Sept. 7, 1965 H. HUBER HIGH-VACUUM PUMP 7 Sheets-Sheet 6 Filed March 30, 1959 INVENTOR H HUBER BY hm/ ATTORNEYS Sept. 7, 1965 H. HUBER 3,204,860

HIGH-VACUUM PUMP Filed March 30, 1959 7 Sheets-Sheet 7 Fig. 12

INVENTOR H" HUBER BY A/m/ ATTORNEYS price of the apparatus.

United States Patent HIGH-VACUUM PUMP Harry Huber, Paris, France, assignor to Compagnie Generale de Telegraphic Sans Fil Filed Mar. 80, 1959, Ser. No. 802,816 Claims priority, application France, Apr. 16, 1958,

24 Claims. (Cl. 230- 69) The present invention relates to high-vacuum pumps of the adsorbing-and-ionizing type, that is to devices operatively connected with envelopes or enclosures operating under high vacuum and intended to improve the vacuum by double eifect of ion pumping, that is, by the capture of positive ions resulting from the ionization of the residual gas molecules within the evacuated envelope and submitted to any suitable electric field, and by the adsorption of the gas molecules on a metal which is evaporated in a continuous manner and of which the condensation is produced in a thin layer on a wall.

Titanium is generally selected as suitable metal for this application by reason of its relatively high chemical activity, especially insofar as the more usual gases are concerned, by reason of the slight vapor pressure of the metallic titanium and of the compounds thereof, and by reason of the stability of the majority of the titanium compounds in the solid form thereof at ordinary temperature.

Several systems of adsorption-and-ionization pump structures are known in the prior art in which, however, either the support of the titanium does not form part of the electrode system participating in the production of ionizing electrons or in which the arrangement necessitates complicated mechanical means to bring the titanium to the evaporation thereof. In both cases, complications in the structure thereof result which adversely affect th The present invention has for its object a pump of the adsorption-and-ionization type which obviates these inconveniences and shortcomings of the prior art.

Another object of the present invention is the provision of a sealed vacuum tube permanently connected to such a pump in order to absorb the fortuitous emission of gases in the course of operation thereof.

The present invention essentially consists in an adsorption-and-ionization pump in which the ion pumping is due to the ionization produced by the circulation of electrons within the electrode system which includes a cathode and an anode connected to suitable supply means sufiicient so that the electrons emitted by this cathode produce a detectable ionization, and in which one of the electrodes of the system is manufactured prior to assembly thereof in the pump, at least in part, of a metal such as titanium which is susceptible to act as getter, this pump being characterised by heating means for the getter up to the point of evaporation thereof.

The invention applies equally to the devices in which the emission of ionizing electrons takes place by the extraction or removal thereof from the cathode by means of an intense electric field in which case the term sufficient supply means connotates a sufficiently high difference of potential applied between the electrodes to produce this phenomenon or to the devices with thermal emission of ionizing electrons in which case the term sufficient supply means connotates a sufiicient intensity of current sent through the heating element of the cathode.

The electrode made of metal such as titanium prior to installation in the pump and susceptible to act as getter may be either the anode or the cathode of the system in which circulate the ionizing electrons. In the former case, the heating of the getter is assured primarily by electron bombardment, but in case of need, a current source might be provided in order to supply an auxiliary heating device of the anode by Joule effect. In the second case, a current source is provided to feed a heating element of the cathode by Joulie effect. This heating may be pushed either only up to the point of evaporation of the getter but below the threshold of thermal-electron emission producing a detachable ionization or beyond this threshold.

In the case in which the getter is supported by the anode, the latter may assume any desired form but in particular it may have the shape of a transparent electrode disposed between the cathode and a wall which is cooled and on which the vapors of the getter will condense. Whatever the shape and form of the anode, a control grid may be interposed between the anode and the cathode in order to control the electron current serving both for purposes of ionization as well as bombardment of the getter, and to thereby regulate the action of the pump by the adjustment of the potential or voltage of this control grid. This potential, by the way, may be controlled automatically in response to the vacuum within the envelope in such a manner as to realize an automatic regulation of the degree of vacuum.

In the case in which the getter is supported by the cathode, a pump of the adsorption-and-ionization type may be provided within the spirit and scope of the present invention which resembles the structure of a Penning gauge or of a known ion pump which is derived therefrom, however, with the difference from this gauge and this pump that the pump operates with a pair of heated cathodes instead of cold cathodes.

Pumps of the adsorption-and-ionization type are also known in the prior art in which an arrangement having a circular symmetry is provided of which the axis extends through a pot or crucible made of graphite, heated by electron bombardment emitted by a cathode surrounding the pot. Two coaxial grids carried at the same positive voltage surround the cathode and thereby form therewith the ionizing system. A titanium wire, moved by any suitable mechanical arrangement, continuously advances up to the point of contact with the pot and evaporates on contact therewith only to condense along a cooled wall.

The different embodiments according to the present invention in which the getter is supported by an anode differ from this prior art construction by the fact that the electron bombardment does not heat a graphite electrode but an electrode made prior to installation in the pump, at least in part of a metal such as titanium which produces within the interior of the pump a reserve of such metal enabling the functioning of the pump during a long time without the need of any mechanical advancing mechanism. The price of the pump in accordance with the present invention is, therefore, considerably reduced as compared to this last-described prior art device and assures increased safety of proper functioning thereof.

Another type of adsorption-and-ionization pump is known in the prior art in which the system of ionization electrodes is constituted by a cathode having thermal emission of electrons and a transparent anode. On the other side of the anode, that is, beyond the ionizing system, is disposed a wire supporting thereon a reserve of titanium and heated up to the point of evaporation thereof but insufiiciently in order that the thermal-electron emission thereof produces a detectable ionization.

The various embodiments according to the present invention in which the getter is supported by the cathode dfiifer from this last-mentioned prior art device by the fact that the reserve of the adsorbing metal is supported by the cathode which pertains to the system in which there exists a circulation of electrons producing a detectable ionization. In this manner, the number of electrodes of the system may be reduced which again simplifies the pump and reduces the ultimate cost thereof.

These and further objects, features and advantages as well as the distinctions of the various embodiments in accordance with the present invention over the known prior art devices described hereinabove will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein:

FIGURE 1 is a longitudinal cross-sectional view of a first embodiment of a pump in accordance with the present invention in which the getter is supported by the anode thereof,

FIGURE 2 is a schematic wiring diagram of the supply voltages for a pump illustrated in FIGURE 1,

FIGURE 3 is a longitudinal cross-sectional view through a modified embodiment of a pump in accordance with the present invention forming a modification of the embodiment illustrated in FIGURE 1,

FIGURE 4 is a longitudinal cross-sectional view through another modified embodiment of a pump in accordance with the present invention utilizing a magnetic field and constituting a modification of the embodiment of FIGURE 1,

FIGURE 5 is a longitudinal cross-sectional view of still another modified embodiment of a pump in accordance with the present invention provided with cold cathodes and constituting a modification of the embodiment of FIGURE 4,

FIGURE 6 is an axial cross-sectional'view of the embodiment of FIGURE 5 essentially perpendicularly to the plane thereof,

FIGURE 7 is a longitudinal cross-sectional view through still another modified embodiment of a pump in accordance with the present invention provided with a control grid and constituting a modified embodiment of FIGURE 1,

FIGURE 8 is a schematic wiring diagram of the supply voltages for the embodiment of the pump of FIG- URE 7,

FIGURE 9 is a diagram showing the results obtained with the pump illustrated in FIGURE 7,

FIGURE 10 is a longitudinal cross-sectional view through another modified embodiment of a pump in accordance with the present invention in which the electrons are emitted from a gun provided with control means formed by a Wehnelt electrode,

FIGURE 11 is a longitudinal cross-sectional view of a modified embodiment of a pump in accordance with the present invention in which the getter is supported at least by one cathode,

accordance with the present invention provided with a filament-type anode and forming a modification of FIG- URE 11.

Referring now to the drawing, wherein like reference numerals are used throughout the various views to designate like parts, and more particularly to FIGURE 1, which shows a pump in longitudinal cross section in accordance with the present invention, reference numeral 1 designates therein a casing or envelope of metallic material and closed oif by a seal 2, for instance, made of glass on which is mounted the system of ionization electrodes which include a filment 3 heated, over connections 4, above the threshold of thermal emission of electrons thereof, and an anode 5 in the; form of a a helix made of titanium and carried at a relatively high voltage by the connection 6 thereof. A jacket 7 for the circulation of water or any other suitable cooling medium is provided around the outer wall of the casing two titanium deposits 22 and 22' are placed along the flat leaving at 9. The envelope 1 is connected at 10 to the casing or enclosure in which it is desired to provide a vacuum. The wall thereof is carried at the potential of the filament 3 or at a potential slightly negative with respect thereto.

FIGURE 2 illustrates the schematic wiring diagram of the device illustrated in FIGURE 1. The filament 3 thereof is supplied from a source 15 connected to the leads 4 while the helix 5 is carried at the anode voltage supplied from source 16 and connected to the lead 6. The filament 3 and the casing or envelope 1 are, for example, connected to ground. As possible modification, an auxiliary connection 17 connected with the helix 5 has been shown in FIGURE 2 and a parallel auxiliary voltage source 18 operatively connected between the connections 6 and 17 is provided therein in order to send through the helix 5 a heating current which produces the evaporation of the getter by the Joule effect thereby supplementing the evaporation due to the electron bombardment.

Operation The pump in accordance with FIGURES 1 and 2 operates as follows:

When the filament 3 is heated and the anode 5 is carried at a high voltage, the electrons emitted by the filament 3 are utilized, on the one hand, to ionize the residual gas molecules and, on the other, to bombard the anode 5, thereby producing the evaporation of the titanium. The evaporated atoms of this metal thereupon Will condense along the wall of the envelope 1 toward which the ions are attracted due to the difference in potential existing between the elements 1 and 5 in such a manner that they are captured thereat by the titanium in the same manner as the non-ionized molecules. A part of the ions is directed also toward the filament 3 and penetrates the same as is the case with the usual ion pumps.

FIGURE 3, in which the same reference numerals are used to designate elements analogous to the embodiment of FIGURE 1, relates to a modification with a plane electrode system. The electrodes 3 and 5, which are represented therein in cross-sectional perspective view, have a different shape from those of FIGURE 1. The filament 3 is a plane spiral and the anode 5, which supports the titanium is a grid parallel to the plane of the filament 3 and essentially perpendicular to the axis of the envelope 1. Otherwise, the operation of the embodiment of FIGURE 3 is identical to FIGURE 1.

In the modified embodiment of FIGURE 4, the filament 3 is arranged perpendicularly to the axis of the envelope 1, whereas the anode 5 supporting thereon the titanium is in the form of a complete cylinder having as its axis the filament 3. A magnetic field directed essentially parallel to the axis of the electrode system is applied thereto by the magnetic poles 21 and 21' of any suitable construction. The electrons emitted by the filament 3 are subjected to the action of the electric field and of the magnetic field which .are mutually crossed. The trajectories or paths of the electrons emitted from the filament 3 are considerably lengthened thereby before arriving at bombarding the anode 5. The ionization output is thereby increased, andthe pumping effect thereof is improved. Otherwise, the operation of the embodiment of FIGURE 3 is identical with that of the preceding embodiments.

FIGURES 5 and 6 represent a modified embodiment along two longitudinally mutually perpendicular crosssectional planes which offers a certain number of differences with respect to the embodiments described hereinabove. The envelope or casing 1 is relatively flat and wall thereof perpendicular to the plane of FIGURE 5, which deposits 22 and 22 operate as cold cathodes, thereby replacing the filament 3 of the preceding embodiments which is obviated thereby. The anode 5 which supports the titanium reserve is a cylinder having an axis perpendicular to the axis of the envelope or casing 1, as in the case of the embodiment of FIGURE 4, but is additionally heated by a heating element 23 fed across the connections 24. The magnetic poles 21 and 21' are provided in the same manner as in FIGURE 4.

FIGURES 5 and 6, therefore, illustrate an embodiment in which the emission of ionizing electrons is effected from cold cathodes when a sufficiently high voltage is applied to the anode 5. The number of electrons emitted is relatively slight, however, since the paths thereof are relatively long along which the electrons circulate within the interior of the cylinder 5- due to the disposition of the two cathodes facing one another and separated by an anode transparent to the electrons and due to the action of the crossed electric and magnetic fields, the ionization is very intense notwithstanding the relatively slight number of emitted electrons. Nonetheless, since this slight number of electrons may be insufficient to carry the titanium on the anode to the temperature of evaporation thereof, the present invention provides an auxiliary heating means of the anode by Joule efiect. Except for the disposition of the getter on the anode and the auxiliary heating thereof, which are characteristic of the present invention, the present arrangement reminds that of the Penning guage of known construction, and the increased ionization effect thereof is obtained in this embodiment according to the present invention by the same mechanism as in this type of guage. Furthermore, the pumping mechanism by adsorption and ionization is the same as in the embodiments of the present invention described hereinabove.

FIGURE 7, in which similar reference numerals have been used to designate parts analogous to that of FIGURE 1, differs principally from FIGURE 1 by the interposition of a control grid 11 supplied across connection 12 and disposed between the filament 3 and the anode 5. Other secondary differences such as the replacement of the cooling jacket 7 by a spiral cooling tube 13 and the arrangement of a bafiie plate 14 in front of the pumping orifice have been shown in connection with this embodiment only to demonstrate the various possibilities of constructions possible in connection with all embodiments of the present invention.

FIGURE 8 represents schematically the wiring diagram of the supply voltage source of the device illustrated in FIGURE 7. The connections or leads 4 are supplied from a source 15 and the connection or lead 6 is connected to the positive terminal of the voltage source 16 which establishes the difference of potential between the anode 5 and the filament 3. The connection or lead 12 is connected, on the one hand, with the envelope 1 and with ground and, on the other, across a resistance 19 to a tap 20 provided on the voltage source 16 which permits to apply a negative voltage to the grid 11 combined with the possibility of adjustment thereof with respect to the filament 3.

The assembly indicated in FIGURES 7 and 8 not only permits a manual adjustment of the electron current emitted by the filament 3 and arriving at the anode 5 and thereby to proportionate the action of the pump, but also constitutes a device in which this action is automatically regulated by the degree of vacuum. In effect, the resistance 19 is traversed in the direction of the arrow by the ion current which is the greater the worse the vacuum. The voltage drop across the resistance 19, therefore, increases with the current which renders the potential of the grid 11 still further positive with respect to the terminal 20. The electron current is therefore, increased, the getter is increasingly evaporated, the action of the pump becomes stronger and the vacuum is improved thereby. Consequently, there is a regulating action in this embodiment which may be stabilized at any desired level. Otherwise, the operation of the embodiment of FIGURES 7 and 8 is identical to that of FIGURE 1.

Actual experience has indicated that a pump constructed in accordance with this principle assures a volumetric pumping rate of 4 to 6 liters per second for pressures inferior to 10 mm. Hg vacuum limit of 10' mm. Hg as shown in the experimental curve of FIGURE 9, which shows the volumetric rate as a function of the pressure plotted along a logarithmic scale. With a reserve of 5 to 6 grams of titanium disposed along the anode helix, and with a bombardment current of milliamperes, it has been possible to operate the pump, taking into consideration the aforementioned figures, over a period superior to more than five hundred hours while maintaining a vacuum of 2 l0 mm. Hg. It is understood, of course, that a control grid may be interposed also in the modification of FIGURE 3.

A control action may be exercised not only by a grid, but also by any other equivalent means.

For example, in FIGURE 10, the electrons are emitted by a gun including a cathode 33 supplied over connection or lead 34 and heated by a filament 35 supplied over connections or leads 36, an accelerating anode 37 supplied by one of the supports 38 thereof and a Wehnelt electrode 39 which has been shown as connected to the envelope 1 which in turn may be grounded. The anode 5 in helix shape which supports the titanium in mounted on anode 37, whereby the structure is reinforced by several support rods 40 which are curved and connected together at the top of the helix. At that point, the structure supports a screen 41 which protects the conduit 10 against projections of the getter material in a manner analogous to the bafile plate 14 of FIGURE 7. The cooling system 7, 8, 9 is similar to that in the preceding FIG- URES l and 4.

In this embodiment, the electrons emitted by the oathode 33 are concentrated into a beam which enters into the interior of the helix 5 of which it bombards the spirals, thereby producing the evaporation of the titanium which is condensed along the walls of the envelope or casing l. The intensity of the beam may be controlled by varying the difference of potential between the cathode 33 and the Wehnelt electrode 39 which eventually produces an auto-regulating action analogous to that of control grid 11 of FIGURE 7.

Furthermore, this arrangement offers the advantage of inherent auto-regulation of the vacuum since, as soon as the vacuum deteriorates, the ion charge produced by the ionizing action of the beam becomes more intense which again increases the concentration of the beam. The unit current density of bombarded surface of the anode 5 become thereby locally greater which increases the evaporation and contributes to the improvement of the vacuum. In order to exploit usefully this effect, a relatively large titanium reserve may be disposed on the last spirals of the helix, for example, by realizing this part of the helix in the form of a wire of larger cross section.

The modified embodiment of FIGURES l1 and 12 illustrates in two mutually perpendicular longitudinal cross sections a modification in which the reserve of titanium is no longer supported by the anode but by at least a cathode of the system adapted to emit ionizing electrons. The embodiment of FIGURES 11 and 12 resembles by its structure the embodiments of FIGURES 5 and 6, that is, a Penning gauge and the ion pump of known construction which is derived therefrom and which does not operate by means of the auxiliary adsorption-type pumping, as is the case in connection with the devices according to the present invention. The anode 5, reduced to a simple turn or loop and without reserve of titanium is disposed between two cathodes 25 and 25' constructed at least in part of titanium and, according to the present invention, heated by a voltage source of any suitable construction, not illustrated herein, and applied respectively between each of the connections 26 and 26', on the one hand, and ground, on the other. The heating thereof may be carried either up to a temperature sufiicient to the evaporation of titanium but insufficient for the production of a detectable ionization by the thermal-electron emission of the cathodes, in which case the cathodes operate from the point of view of production of ionizing electrons as cold cathodes or up to a temperature passing beyond the ionization threshold, in which case the cathodes are hot cathodes. In both cases the increased ionization is produced by the mechanism of the Penning gauge under the action of the magnetic field produced by magnet poles 21 and 21', whereas the pumping by adsorption and ionization takes place as in the embodiments described hereinabove and in particular in the pump according to FIGURES and 6.

FIGURE 13 shows still another modification of the present invention in which the reserve of titanium is supported by the cathode or by several cathodes, this variation constituting the modification of an ion gauge known per se.

This known structure includes a filament anode 5, disposed within the axis of the envelope or casing 1 separated into several compartments by the transverse discs 27 provided in the center thereof with apertures to permit the passage of the anode, the entire assembly being placed in an axial magnetic field produced by the coil 28. According to the present invention, the discs 27 include auxiliary apertures 29 across which a certain nurriher of filaments 30 pass which are distributed over the periphery thereof and support each a titanium spiral constituting the reserve of the getter. These filaments 30 are suspended by springs 31 and supplied across connections 32, the voltage being applied between each of these connections 32 and ground. The anodeS is supplied across connection 6 as in the preceding embodiments. Also, as with the preceding embodiments, a cooling system 7, 8, 9 is provided. As in FIGURE 11, the filaments 30 may be heated either up to the point of evaporation of the titanium or therebeyond up to the point of thermal production of ionizing electrons. From the point of view of ionization, this embodiment functions as an ion gauge of known construction which, however, owing to the modifications introduced in accordance with the present invention operates, on the other hand, as a pump of the adsorption-and-ionization type thereby entailing the advantages obtainable with the modifications described hereinabove.

The foregoing description illustrates clearly the large number of possibilities of construction according to the present invention, it being understood that any variation known to a person skilled in the art which follows from the examples illustrated herein and which utilize the principles disclosed therein is to be considered as encompassed by the scope of the present invention.

Thus, it is obvious that the present invention is not limited to the specific embodiments described and shown herein but is susceptible of many changes and modifications within the spirit and scope of the present invention. For example, the present invention is also applicable to installations in which a pump of the type described is incorporated or permanently associated with a sealed vacuum tube to absorb the fortuitous emission of gases during the course of operation thereof. Consequently, I do not wish to be limited to the details described and illustrated herein, but intend to cover, all such modifications and changes as are encompassed by the scope of the appended claims.

I claim:

1. A high-vacuum pump of the adsorbing-and-ionizing type, comprising an envelope, means for cooling the walls of said envelope, and an electrode system within said envelope, said system including at least a cathode electrode and an anode electrode, one of said cathode and anode electrodes being made, at least in part, of a gettering metal, means for heating said one electrode 'to evaporate said gettering metal, and supply means for said cathode and anode electrodes to produce by the electrons emitted from said cathode electrode a detectable ionization of residual gas molecules within said envelope.

2. A pump as claimed in claim 1, wherein titanium is used as said gettering metal, and wherein said one electrode is made of said gettering metal prior to mounting thereof in the envelope.

3. A pump as claimed in claim 1, wherein said supply means provides a potential difference between said anode and cathode electrodes sufliciently high for producing cold electron emission by said cathode electrode.

4. A pump as claimed in claim 1, wherein said supply means provides a heating current of said cathode electrode suficiently high for producing hot electron emission therefrom.

5. A pump as claimed in claim 1, wherein said getter metal is at least a part of said anode electrode, and wherein said anode electrode is heated by bombardment of electrons emitted from said cathode electrode.

6. A pump as claimed in claim 5, comprising additional heating means for said anode electrode utilizing the Joule effect.

7. A pump as claimed in claim 1, wherein said getter metal is at least a part of said cathode electrode, and wherein said heating means uses the Joule effect.

8. A pump as claimed in claim 7, wherein said heating means are effective to evaporate said getter metal but ineffective to provide hot electron emission from said cathode electrode of such a strength that detectable ionization of residual gas molecules is thereby produced.

9. A pump as claimed in claim 7, wherein said heating means are effective to provide hot electron emission from said cathode electrode of such a strength that detectable ionization of residual gas molecules is thereby produced, and said gettering metal is also evaporated.

10. A pump as claimed in claim 1, wherein said anode electrode is a transparent structure, located between said cathode electrode and said cooled wall of said envelope.

11. A pump as claimed in claim 1, wherein said electrode system comprises a control grid between said anode electrode and said cathode electrode.

12. A pump as claimed in claim 11, further comprising means for controlling said control grid potential with respect to said cathode electrode potential by the vacuum pressure within said envelope.

13. A pump as claimed in claim 12, wherein said control grid is connected to the potential of a cooled wall of said envelope, and further comprising a circuit including a series resistor to vary the potential of said cathode electrode in dependence of the ion current in said cooled wall.

14. A pump as claimed in claim 5, wherein said anode electrode is a cylinder surrounding said cathode electrode, and wherein means providing a magnetic field are disposed to direct the magnetic lines of force thereof in the axial direction of said cylinder. 7

15. A pump as claimed in claim 3, wherein said cathode electrode is formed by at least one cold-electron emissive layer dis osed on said cooled wall.

16. A pump as claimed in claim 15, wherein said anode electrode is a cylinder having its axis normal to said cathode electrode surface, and further comprising means providing a magnetic field to direct the magnetic lines of force thereof in the direction of said axis.

17. A pump as claimed in claim 16, comprising additional heating means for said anode electrode utilizing the Joule eifect.

18. A pump as claimed in claim 15, wherein said envelope has two parallel walls, said emissive layers being disposed on said walls.

19. A pump as claimed in claim 1, wherein said electrode system further comprises electron gun means including a Wehnelt electrode, and means for controlling the potential of said Wehnelt electrode.

posed on both sides of a transparent anode electrode, and further comprising means providing a magnetic field to direct the magnetic lines of force thereof in the direction from one of said cathode electrodes to the other.

21. A pump as claimed in claim 7, wherein said anode electrode is a filament disposed in the axis of said envelope, and further comprising a plurality of getter metal bearing cathode electrodes extending parallel to said axis and surrounding said anode electrode, and means to direct magnetic field lines of force in the direction of said axis.

22. A pump as claimed in claim 21, wherein transverse walls are disposed within said envelope to subdivide the interior thereof into a plurality of compartments, apertures being provided in said transverse walls to enable passage therethrough of said filamentary anode electrode and said plurality of cathode electrodes.

23. A high-vacuum pump of the adsorbing-and-ionizing type comprising an envelope, means for cooling the walls of said envelope, and electrode means within said envelope including at least a cathode electrode and an anode electrode, one of said cathode and anode electrode being made at least in part of a getter material, means for operating said one electrode to effectively evaporate 1% said getter material, and supply means for said cathode and anode electrodes to produce by the electrons emitted from said cathode electrode a detectable ionization of residual gas molecules within said envelope.

24. An ion pump comprising an envelope, a ring- :shaped anode within said envelope, an incandescible cathode comprising two portions disposed on opposite sides of the plane of the anode, at least one of said cathode portions being provided with a supply of gas-binding metal which is evaporated during operation of the cathode which is precipitated on the wall of the envelope, and means to produce a magnetic field the lines of force of which extend between the portions of the cathode.

References Cited by the Examiner UNITED STATES PATENTS 2,925,214 2/60 Gurewitsch et al. 23069 FOREIGN PATENTS 797,232 6/58 Great Britain.

LAURENCE V. EFNER, Primary Examiner.

WARREN M. BAMFORD, JOSEPH H. BRANSON, JR.,

WARREN E. COLEMAN, Examiners. 

1. A HIGH-VACUUM PUMP OF THE ADSORBING-AND-IONIZING TYPE, COMPRISING AN ENVELOPE, MEANS FOR COOLING THE WALLS OF SAID ENVELOPE, AND AN ELECTRODE SYTEM WITHIN SAID ENVELOPE, SAID SYSTEM INCLUDING AT LEAST A CATHODE ELECTRODE AND AN ANODE ELECTRODE, ONE OF SAID CATHODE AND ANODE ELECTRODES BEING MADE, AT LEAST IN PART, OF A GETTERING METAL, MEANS FOR HEATING SAID ONE ELECTRODE TO EVAPORATE SAID GETTERING METAL, AND SUPPLY MEANS FOR SAID CATHODE AND ANODE ELECTRODES TO PRODUCE BY THE ELECTRONS EMITTED FROM SAID CATHODE ELECTRODE A DETACTABLE IONIZATION OF RESIDUAL GAS MOLECULES WITHIN SAID ENVELOPE. 